Strain gage based pressure transducers are used to measure pressures, such as the pressure of fluids in a vehicle. A strain gage based pressure transducer that utilizes an integrated Wheatstone bridge exhibits a high over pressure capability, high output, low zero offset and linear output.
Conventional pressure transducers typically utilize four stain gages bonded to the diaphragm of a metal pressure port. As is well known in the art, the gages are positioned on the diaphragm in such a way that two strain gages are put into compression and two strain gages are put into tension when pressure is applied to the diaphragm.
Currently, the process for producing a pressure transducer on a machined metal pressure port having a thin diaphragm on the top surface is to first bead/sand blast the top surface of the pressure port to roughen the surface in order to keep the glass from flowing out and becoming too thin. The pressure port is put through a cleaning cycle to remove any particles from the port that may result from the bead/sand blasting. The glass frit is then screened printed at two separate locations on the top surface of the pressure port. The pressure port is passed through a furnace to fire the glass frit. Two half bridge strain gages are then placed on top of the fired glass fit. The pressure port is again passed through a furnace to embed the strain gages into the glass. Six wire bonds are made between the strain gages and an interface printed circuit board (PCB) to form a Wheatstone bridge circuit.
The aforementioned process results in puddling of the glass frit on the diaphragm, non-uniform glass thickness and concomitant breakdown voltage control problems, dirt and debris resulting from the bead blasting process, and other processing inefficiencies and drawbacks. Alternative apparatus and methods for forming a pressure transducer are desired.